Probiotics are living microorganisms that can affect
the host in a beneficial manner. Prebiotics are nondigestible
food ingredients that stimulate the growth and activity
of probiotic bacteria already established in the colon.
Efficacy of probiotic compounds has been shown in a
wide range of gastrointestinal diseases. Lactobacillus
GG alone, or the combination of Bifidobacterium
bifidum and Streptococcus thermophilus, is
effective in the treatment of Clostridium difficile,
as well as in preventing the frequency and severity
of infectious acute diarrhea in children. Prevention
of antibiotic-induced diarrhea with the concomitant
administration of either Lactobacillus GG or
Saccharomyces boulardii has been demonstrated.
The most successful studies involve the use of Lactobacillus
GG at a dose of 1×1010 viable organisms
per day and the yeast boulardii at a dose of
1 g/day. A probiotic preparation (VSL#3 - 6 g/day) that
uses a combination of three species of Bifidobacterium,
four strains of Lactobacillus and one strain
of Streptocccus has shown promise in maintaining
remission in ulcerative colitis and pouchitis, as well
as in preventing the postoperative recurrence of Crohn's
disease. The mechanism of action of probiotics may include
receptor competition, effects on mucin secretion or
probiotic immunomodulation of gut-associated lymphoid
tissue. Oral administration of probiotic compounds has
been demonstrated to be well tolerated and safe. However,
while probiotics have the potential to improve human
health and to prevent and treat some diseases, major
improvements are needed in labelling and quality assurance
procedures for probiotic compounds. In addition, well
planned and controlled clinical studies are necessary
to delineate fully the potential for probiotic compounds.